Current two-piece ostmomy couplings generally require axial compressive force to secure a pouch ring to a faceplate ring. The application of axial force can cause wearer discomfort, since it ordinarily involves pressing the rings together against the body wall in the sensitive peristomal area, and may also be ineffective in producing proper latching and sealing engagement between the two coupling rings. Such rings can be unknowingly misaligned, resulting in accidental and/or premature disengagement. Also, the ability of conventional rings to produce an effective seal generally depends upon the extent of circumferential compression of the faceplate ring by the pouch ring. Typically, an element of the pouch ring stretches or deforms as it is applied over the faceplate ring, bringing such surfaces into leakproof contact. The problem has been to compromise the amount of circumferential compression (and therefore seal integrity) in order to ease the force required to fit a pouch ring into sealing engagement with a faceplate ring.
The present invention addresses this problem by providing one of the components, preferably the pouch component, with a coupling ring that is capable of being flexed into each of two stable conditions or states. In one such state, which may be considered the ring's normal untensioned state, the inside diameter of the ring is reduced to produce a fluid-tight circumferential seal about the mating part of the other coupling ring, whereas in its other state, the bistable ring has an enlarged inside diameter that facilitates joining of the coupling rings together. Thus, in use, the pouch coupling ring is flexed into its stable expanded (and tensioned) state so that little if any axial force is needed to fit the rings together and then, once the rings are in position, the bistable ring is simply flexed into its normal state of reduced inside diameter to produce fluid-tight interlocking engagement between the parts.
In its normal state, the bistable coupling ring is generally frusto-conical with the slope of its flange portion extending outwardly in one axial direction (preferably outwardly and away from the pouch upon which such a ring is mounted), whereas in its tensioned state of reduced inside diameter the ring is also frusto-conical but the direction of slope is reversed (i.e., axially outwardly towards the pouch). The inner periphery of the ring is circular in outline and rounded in axial section to provide a smooth annular lip for sealing engagement about that portion of the companion ring received in the opening. To maximize the difference between the inside diameters in the two stable states, the contractable/expandable coupling ring is provided with an integral rib located adjacent the sealing lip on the convex side of the ring when that ring is in its normal, untensioned condition. An integral tab portion may project radially outwardly beyond the circular outer periphery of the ring to facilitate manually directing the ring into each of its two stable states.
Other features, advantages, and objects will become apparent from the specification and drawings.